Gerotor Pump Performance Correlation Study Version 2.0

www.gerotordesignstudio.comGerotor Design Studio Ltd

Unit 8 Sumner Point, Lancashire Business Park, Enterprise Drive, Leyland PR26 6TZ

Company Number: 10609806

Gerotor Pump Performance Correlation Study – Version 2.0.30

17/03/2016

Correlated Pumps:

•Bosch Rexroth PGZ4

•Size ’80’ – Model PGZ4-1X/080RA07VE4

•Parker Hannifin PGG20010

•Miniature Gerotor – Fluid Power Research Laboratory, University of Turin, Italy

www.gerotordesignstudio.com

Bosch Rexroth PGZ4

Model PGZ4-1X/080RA07VE4


Bosch Rexroth PGZ4 Series:

•Fixed Displacement (no pressure relief valve)

•Single sided porting, but with Shadow Porting feature

•8 lobes Inner / 9 lobes Outer

•Information from www.boschrexroth.com


Bosch Rexroth PGZ4 Series: www.gerotordesignstudio.com

Bosch Rexroth PGZ4-1X/080RA07VE4:

Build of GDS model – Gerotor Design

To acquire unknown

dimensions, scaling of the

provided drawings had to be

used.

For example, the rotor OD was

derived from the given

dimension of the pump external

mounting nose.

Dimensions acquired by this

method:

•Outer Rotor Diameter

•Eccentricity

•Rotor Thickness (using L1 and

L2 dimensions on drawings)

•Shaft Diameter (‘driving disk’)


Actual Port Design was not known, therefore

the GDS ‘Design Ports’ feature was used to

generate porting based on the gerotor

dimensions.


Build of GDS model – Porting Design

Shadow porting is evident

from the sectional drawings


Hydraulic Fluid Properties taken from Mobil 1 DTE10

data sheet (meets specification of Rexroth RE 90220)

Pump speed and pressure ranges taken to match

performance parameters from Rexroth technical

specification sheet


Build of GDS model – Fluid / Material / Pump Properties


From www.wolfram.com website

From Mobil 1

DTE10 MSDS

•Youngs Modulus from www.engineeringtoolbox.com

•Value is for high strength steel at 20-90°C

•Poissons Ratio from www.engineeringtoolbox.com

•Value is for high strength steel

•Coefficient of Friction from average of internet sources

(dynamic friction; steel and lubricated aluminium)


Build of GDS modelBuild of GDS model – Fluid / Material / Pump Properties


http://www.engineeringtoolbox.com/

http://www.engineeringtoolbox.com/


Results – Flow and Drive Power

0

500

1000

1500

2000

2500

3000

3500

0 200000 400000 600000 800000 1000000 1200000

Pump Delivery Pressure (Pa)

Po

wer

to T

urn

(W

) 200

450

700

950

1200

1450

0

20

40

60

80

100

120

140

0 200000 400000 600000 800000 1000000 1200000


Flo

w (

lit/

min

)

200

450

700

950

1200

1450

1134 W

2994 W

116.94 litres / min


Parker Hannifin

Model PGG20010


Parker Hannifin PGG20010:

•Series of pumps based on same basic dimensions

•Only dimension change is length (X and Y values)

•Conclude that rotor set is the same, only different in length

•Plot of Displacement vs Length shows linear relationship

•Theoretical ‘zero’ displacement is at X=66.5mm

•Therefore rotor length for PGG20010 pump should be

•72.6-66.5 = 6.1mm

PGG200xx Pump Length vs Displacement

y = 27.478x + 66.51

70

72

74

76

78

80

82

84

86

88

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8

Displacement (cu in / rev)

"X"

dim

en

sio

n (

mm

)



•Pump will undoubtedly have Nichols Portland Gerotor set

•NP are part of the Parker Hannifin group

•Examination of NP standard gerotor sets shows 2 likely candidates

for gerotor forms:

•4086 – 4 x inner lobes; 0.86in3/rev per inch of length

•6095 – 6 x inner lobes; 0.95in3/rev per inch of length

•However, 6095 has minimum OD of 57.10mm

•Likely not to fit inside pump housing (from scaling of

drawings)

Pump

Size

Displacement

(in3/rev)

"X"

Dimension Delta "X" Comments

0 0 66.5 0 From calculation

10 0.218 72.6 6.1

0.218cuin for 6.1mm

length = 0.908cuin/inch

20 0.45 78.7 6.1

0.232cuin for 6.1mm


30 0.7 85.8 7.1

0.25cuin for 7.1mm


57.10mm rotor set would allow

no clearance to bolt bosses.

Therefore assumption is 4086

rotor set is used for PGG20010

(diameter 50.01mm)


Build of GDS model – Gerotor DesignTip and axial clearances obtained from

Nichols Portland design guidelines

“Gerotor Selection & Pump Design v1.2”


Rotor Thickness greater than calculated

6.1mm.

To obtain a displacement of 0.700cuin/rev

with this gerotor set, a thickness of 21mm

is required (i.e. for ’30’ size pump).

Therefore an assumption of 7mm was used

for this ’10’ size pump.

This gives a theoretical ‘over capacity’

(0.236cu in/rev) but will compensate for

greater leakage losses with a smaller

gerotor, so would be feasible for the actual

pumping elements.


Actual Port Design was not known, therefore

the GDS ‘Design Ports’ feature was used to

generate porting based on the gerotor

dimensions.

Build of GDS model – Porting Design

Shadow porting is not shown on any sectional drawings,

but is assumed based on the recommendation given in the

Nichols Portland’s own design guide

Parker Hannifin PGG20010: www.gerotordesignstudio.com

Only fluid property given in the Parker Hannifin product

guide is a viscosity of 32cSt, for determination of the flow

characteristics.

All other fluid and material properties were assumed to be

as for the Bosch Rexroth pump design

Speed and pressure ranges taken to be consistent with the

pump performance characteristics published by Parker

Hannifin

Build of GDS model – Fluid / Material / Pump Properties

Parker Hannifin PGG20010: www.gerotordesignstudio.com

Results – Flow and Drive Power


0

2

4

6

8

10

12

14

0 2000000 4000000 6000000 8000000 10000000 12000000 14000000 16000000


Flo

w (

lit/

min

)

1000

1500

2000

2500

3000

3500

Characteristic

PGG20010

Results

GDS

Results Difference Error (%)

Flow @ 3500rpm

34.5bar 12.5 12.67 0.17 1.36

Flow @ 3500rpm

138bar 9.16 10.09 0.93 10.15

Flow @ 1000rpm

34.5bar 3.33 3.02 -0.31 -9.31

Flow @ 1000rpm

138bar 0.25 0.4 0.15 60.00

Power @ 3500rpm

34.5bar 973 1069 96 9.87

Power @ 3500rpm

138bar 3252 3444 192 5.90

Power @ 1000rpm

34.5bar 324 246 -78 -24.07

Power @ 1000rpm

138bar 1005 924 -81 -8.06

0

500

1000

1500

2000

2500

3000

3500

4000

0 2000000 4000000 6000000 8000000 1000000

0

1200000

0

1400000

0

1600000

0


Po

wer

to T

urn

(W

) 1000

1500

2000

2500

3000

3500


Miniature Gerotor – Fluid Power Research Laboratory, University of Turin, Italy

“Miniature Gerotor Pump Prototype for Automotive Applications” – S. Manco; N. Nervegna; M. Rundo; M.

Margaria

The Fluid Power Research Laboratory at Polytechnic of Turin, Italy

Presented at 3rd International Fluid Power Conference, March 5-6 2002, Aachen, Germany


Miniature Gerotor Pump Prototype:

Pump Specifications

• Assumed working fluid: DOT4 Brake Fluid

Known parameters:

•Required volume

•No. Outer Lobes

•Thickness

•Outer Diameter

‘Design Rotors’ feature used to create

remaining design parameters

•Iterations of Eccentricity and Radius

Inner Root used to bring Approx

Capacity into correct range (allowance

for some leakage loss)

Very small Gerotor



Pump Specifications

Porting designed using GDS ‘Design Ports’ feature

No shadow porting or double sided porting selected

Content of part of the technical paper was to show

the effect of ‘balance plates’ on volumetric efficiency.

The balance plates allow high pressure fluid behind

the rotor housing to close the axial clearance gap at

high pressures (reduce leakages) – but it still allows a

rotor to housing contact, so is not the same as

shadow or double sided porting! Hence the boxes are

not checked.

DOT4 Fluid Properties

Values used are assumed the

same as for other pump designs

– no indication given in the

technical paper for other values



Results

84

86

88

90

92

94

96

98

100

0 1000000 2000000 3000000 4000000 5000000 6000000 7000000


Vo

lum

etr

ic E

ffic

ien

cy (

%)

1500

1800

2100

2400

2700

3000

•GDS assumes the outer rotor remains concentric to the housing

bore at all times

•Therefore the results of ‘Radial Load’ compensation are

meaningless in GDS and the results should be compared to

the highest level of radial compensation tested in the

technical paper (assumption is this is closest to the

concentric condition)

88%

90%


0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0 1000000 2000000 3000000 4000000 5000000 6000000 7000000


To

rqu

e t

o T

urn

(N

m)

1500

1800

2100

2400

2700

3000


Results

•The values for drive torque are not as aligned as with the larger

rotor sets

•Slope of the line is different (see next slide) and would normally cut

the Y axis at 0 torque, however the results from the actual tests

show a torque of 0.14Nm at no delivery pressure

•Possibly cause is a high friction (seals or the radial

compensation mechanism used in the experiment) which is

not modelled in GDS

0.48Nm

0.55Nm @ 50bar

Data from

tech. paper


0

0.1

0.2

0.3

0.4

0.5

0.6

0 1000000 2000000 3000000 4000000 5000000 6000000 7000000


To

rqu

e t

o T

urn

(N

m)

1500

1800

2100

2400

2700

3000


Results

•The slope of the Torque vs Pressure line is directly related to the friction in the system

•Friction for a non shadow or double-ported pump is mainly dictated by the face friction

•By changing the value of the coefficient of friction in GDS to 0.04 the slope of the line is replicated, however the offset of 0.14Nm

still exists (other, non pump related friction as previously mentioned)


Summary


Summary:

Rexroth PGZ4-80 Parker PGG20010 Miniature Gerotor

Displacement 84.2 0.218 0.17

Shaft Diameter 42 12.7 5

Thickness 39 7 3.8

Outer Rotor OD 110 50.01 23

Number of Lobes 9 5 13

Rotor Tip Clearance 0.1 0.08 0.002

Axial Clearance 0.07 0.03 0.01

Eccentricity 4.4 2.819 0.5

Radius of Inner Rotor Root 35 12.9 7.25

Radius of Outer Rotor Lobes 20 12.7 1.5

Porting Geometry (detailed) NO NO NO

Shadow or Double Porting? YES YES YES

Fluid Properties YES NO NO

Material Properties NO NO NO

Coefficient of Friction NO NO NO

Speed Range YES YES YES

Pressure Range YES YES YES

High Influence for Non Shadow or Non Double Ported Applications

for Power Consumption

High Influence for Volumetric Efficiency and Power Consumption

Direct influence on Capacity


High Influence for Volumetric Efficiency

Affects Capacity and Power Consumption

BLACK text = Known Parameter for this study

RED text = Unknown Parameter for this study

LARGE text = Big influence on the calculated results


Summary:

Rexroth PGZ4-80

Displacement 84.2

Shaft Diameter 42

Thickness 39

Outer Rotor OD 110

Number of Lobes 9

Rotor Tip Clearance 0.1

Axial Clearance 0.07

Eccentricity 4.4

Radius of Inner Rotor Root 35

Radius of Outer Rotor Lobes 20

Porting Geometry (detailed) NO

Shadow or Double Porting? YES

Fluid Properties YES

Material Properties NO

Coefficient of Friction NO

Speed Range YES

Pressure Range YES







Very good correlation of results to published figures

•~1% error for flow and power consumption

•Rotor thickness not known precisely, but derived from scaling of given dimensions

and other pump sizes in the PGZ4 family

•Tip and axial clearances taken from other pumps of similar size


Summary:

Parker PGG20010

Displacement 0.218

Shaft Diameter 12.7

Thickness 7

Outer Rotor OD 50.01

Number of Lobes 5



Eccentricity 2.819

Radius of Inner Rotor Root 12.9

Radius of Outer Rotor Lobes 12.7



Fluid Properties NO



Speed Range YES

Pressure Range YES






Good correlation of results to published figures

•<10% error for flow and power consumption

•Greater %age errors at lower value results (normal)

•Main assumption for this model was that a 4086 rotor set was used

•Values could be very different if a different rotor set is actually used!


Summary:

Miniature Gerotor

Displacement 0.17

Shaft Diameter 5

Thickness 3.8

Outer Rotor OD 23

Number of Lobes 13



Eccentricity 0.5

Radius of Inner Rotor Root 7.25

Radius of Outer Rotor Lobes 1.5



Fluid Properties NO



Speed Range YES

Pressure Range YES

High Influence for Non Shadow or Non Double Ported Applications

for Power Consumption


Direct influence on Capacity





Possibly too many unknowns for accurate simulation…

•Actual tip clearance not known but assumed very small

•Small gerotor size means incorrect data can have

bigger influence on the results, especially at low

speeds and flows

•Study with actual gerotor set included radial

compensation via application of load to the outer rotor –

affects drive torque significantly

•Coefficient of friction not known due to little detail on

housing material and unknown influence of ‘balance

plates’

•General ‘trend’ of results is still valid, if not

absolute values


Gerotor Pump Performance Correlation Study Version 2.0

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